The selection of a floor covering is generally based upon a combination of factors including aesthetic features, such as the look and feel of the floor covering, and functional features, such as retention of surface appearance, stain resistance, moisture resistance, ease of cleaning, and resistance to dirt build-up. For example, floor covering installations prone to high traffic, dust and dirt collection, or to moisture or stains, such as in kitchens, generally use solid materials such as wood, metals, ceramic tile, vinyl or rubber. These products retain their surface appearance after heavy use, are simple to keep clean, and are less prone to harboring bacterial growth. Moreover, they are suitable for modular or tile installations, because they are relatively stiff, and, most preferably, dimensionally stable. These attributes permit the floor coverings to be evenly secured to the floor, and to lay flat and remain flat during use as temperature and humidity vary with time, a property known as “lay-flat”. However, these products lack the textile look, softness or sound dampening qualities of textile products.
FIG. 1 prepared by the present inventor graphically and schematically summarizes floor covering technology offering cushion, softness and sound dampening along with a fibrous/textile surface. Durability varies and it is not plotted. Products are grouped by two factors: planar gather and face stretch. The grouping is for illustrative purposes only, indicating the direction of property change. Properties are not plotted to scale. Group A in the center includes the most common types of textile-faced floor coverings. They generally lack the superior stability of the solid floorcoverings because they are, in general, built with layers of organic or polymeric materials and, as the layers expand or contract at different rates with temperature or humidity, the composites tend to deform out of plane. They also allow very limited gather, i.e. limited planar contraction, and limited surface stretch. For these types of textile structures the capability to gather planarly is desirable, because it would allow the structure to accommodate lateral stresses created when the composite tries to expand while confined between walls or tiles on the floor, and minimize the tendency to buckle or warp out-of-plane. Low face stretch is also desirable so that the floorcovering does not develop resistance to forward foot, furniture or cart motion, and/or it does not delaminate due to repeated face stretch with traffic. Floor coverings in Group A include conventional carpets with relatively deep cushioning piles prepared by tufting, knitting, stitchbonding, knotting or weaving, as well as laminates of thin textile fabrics bonded to cushioning backings.
Group B, placed in the upper left hand group of FIG. 1 emulates the solid, stable floorcoverings. In general it includes floorcoverings similar to those in Group A with added reinforcement, using stiff and/or heavy sub-layers and/or extra adhesive, to stabilize the structure and essentially eliminate both surface stretch and gather.
Group C, placed in the lower right-hand group, is an attempt in the opposite direction, wherein a floorcovering is composed of a highly-elastic textile face layer attached to an elastic cushion allowing high gather as well as high stretch. Such a floorcovering is undesirable in high-wear commercial, institutional or other such applications, because traffic is impeded by the stretchy surface and repeated stretch can cause delamination with heavy use. Group C floorcoverings may be too elastic to resist foot traffic.
Group D represents textile-faced floorcoverings with high face layer stretch and virtually no gather. Such floorcoverings are undesirable, because they would be too elastic/stretchy to walk on and would also buckle out-of-plane due to low gathering. No products of this nature have been developed in prior art.
Group E goes in the opposite direction and includes preferred textile-faced floor coverings that are both easy to walk on, i.e., have low face layer stretch, and would not buckle out-of-plane because they have the ability to contract and expand, i.e., high gather. The group includes laminates by the present inventor having planarly-gatherable undulating thin fabric faces joined to compliant cushioning backings.
The traditional deep cushioning-pile products within Group A of FIG. 1 include tufted, knitted, stitched, knotted, or woven pile structures. They provide softness, cushion, and a limited level of abrasion and wear resistance. Compared to rigid solid-surfaced products they are less durable. Deep cushioning-pile products also tend to lose their texture and their cushion with heavy use. This occurs because their piles become “matted”, as they are bent and crushed with heavy traffic. Denser and shorter piles may increase the durability of these products at the expense of cushion. Many deep-pile structures are also generally prone to unraveling at cut edges, requiring heavy fortification in modular or tile applications. Additionally the spaces between the upstanding piles tend to collect dust and dirt, allowing the growth of bacteria, making the floor-covering difficult to clean and sanitize. To stay flat, most broadloom carpets of this type are stretched and held at the edges of the room with pin-plates, Velcro™, and/or other similar means in order to hold the pre-stretched carpeting. If the product is used as a modular tile, deep cushioning pile structures are reinforced with heavy and stiff backings or with added stiff yarns, as exemplified by Justesen U.S. Pat. No. 5,902,663, Irwin U.S. Pat. No. 5,962,101, and Schilling U.S. Pat. No. 6,162,748, as shown in Group B in FIG. 1. The added backings dominate the thermal and hygroscopic characteristics of the composite in order to help the composite remain flat on the floor despite changes in temperature and/or humidity.
The remainder of the floorcoverings shown in Group A in FIG. 1 include relatively thin textile fabrics laminated to soft and thick resilient backings. They provide dirt-blocking and textile face aesthetics along with cushion. For the sake of durability and abrasion resistance the face fabric is a “velours”, velvet or similar structure with the face fibers upstanding or looping at the surface. The upstanding or looping fibers are held in place or “anchored” with fibrous or polymeric “base” or “anchoring” sublayers that stabilize the fabric, but increase the tendency of the denser face layer to expand and contract much faster than the softer cushion as temperature and humidity varies. Consequently the thermal and hygroscopic properties of the relatively dense face layers are not balanced against the thermal and hygroscopic properties of the bulky cushioning backings. Small amounts of differential expansion or contraction can cause major warping, with the edges and corners rising over the center (cupping), or the center rising over the edges and corners (doming). Differential expansion or contraction of the floor covering as low as 1% can cause dramatic warping by a height approximately equal to 10% of the length or width of the floor covering. Composite floorcoverings using shallow-pile face fabrics containing dense anchoring base sublayers are disclosed in U.S. Pat. No. 3,066,513 to Leybourne, U.S. Pat. No. 3,576,701 to Salamon, and U.S. Pat. No. 7,622,408 to Zafiroglu, among others, as shown in FIG. 1. Similar fabrics, not necessarily intended for floorcovering composites, are also disclosed in U.S. Pat. No. 529,858, to Hardwick, U.S. Pat. No. 3,254,510 to Lesley, U.S. Pat. No. 4,284,507 to Beane, U.S. Pat. No. 4,406,309 to Czelusnik, and U.S. Pat. No. 3,732,708 to Troy.
U.S. Pat. Nos. 6,936,327 and 7,255,761 to Zafiroglu, the present inventor, are also listed in Group A in FIG. 1, and incorporated by reference herein in their entirety. They disclose stitchbonded fabrics using shrinkable substrates designed to cause the stitching yarns to buckle out of plane and form pile-like loops. The shrunk substrates remain within the fabric structure, stabilize the fabric and hold the buckled yarns in position, serving the same function as the fibrous anchoring base sub-layers of the shallow-pile fabrics discussed above. The shrunk fabrics may be attached as they are to a soft cushion layer without additional processing steps to form floor-coverings. The lay-flat properties of such floorcoverings are not discussed.
Another U.S. Pat. No. 3,985,925 to Lefebvre, also shown in Group A in FIG. 1, envisions a mechanism similar to fabric stabilization for the sake of durability. Very light woven or knit face “velvet” face fabrics weighing only between 70 and 120 g/m2 are attached to dense sublayers, in the range of 1,000-1,200 kg/m3 (1.0-1.2 g/cc), which are in turn attached to or co-formed with less and less dense secondary cushioning sublayers. Details of the construction of the fabrics or the expected level of durability are not discussed, and no provision is made for layflat. A dense sublayer directly glued to a very light fabric having a very limited weight of “pile” fibers would severely limit facial aesthetics, and have quite limited abrasion resistance. It would also dominate expansion and contraction and make it difficult to control layflat.
Other approaches have been proposed in prior art dealing with thin face fabrics attached to soft cushion layers; U.S. Pat. No. 2,688,578 to Teague shown as part of Group C in FIG. 1 goes in the opposite direction and proposes a durable floor covering prepared by laminating a relatively thin and highly-stretchable elastic face fabric to an elastic backing with highly-elastic adhesives. Preferred elastic face fabrics include inelastic fabrics coated or impregnated with elastic polymers. The face is required to stretch by at least 15% and preferably up to 50% to simulate the lateral deflection of the upstanding pile yarns of deep-pile floor coverings. However, unlike the action of deep pile tufts which can bend forward without impeding forward foot or roller or caster motion, a highly elastic face can increase drag against traffic, and in instances of high traffic it can result in excessive surface fiber fatigue and delamination due to repetitive stretching. A highly deformable elastic face can particularly increase resistance to sliding chairs across the floor, which is already a problem with the majority of pile carpeting. Walking on a highly stretchable face fabric is difficult due to the unstable nature of the highly stretchable surface. Moreover the construction of the face fabrics, the orientation of the surface fibers, the level of fibrous surface quality after the application of adhesive, or the targeted level of durability are not disclosed, and no provision is made for lay-flat.
As shown in Group E of FIG. 1, a different concept for simultaneously improving the dimensional stability, lay-flat, and durability for floor-coverings using textile fabrics attached to cushioning layers, without adding stiff under-layers under the textile face, is disclosed in U.S. Pat. Nos. 7,425,359 and 7,431,975 to Zafiroglu, the present inventor, and are incorporated herein in their entirety. They utilize deeply-structured three-dimensional undulated surfaces, automatically accommodating planar stress by acting as planarly-extensible and compressible spring-like layers, and by distributing surface expansion and contraction along the facial undulations, and virtually eliminating deformation out-of-plane. U.S. published patent application US 2009/0047465, also by the present inventor and hereby incorporated by reference in its entirety, extends the concept to more durable embodiments by requiring substantially continuous adhesion, along the undulations. The undulating surface approach, however, limits the possibility of a floor-covering with a smooth-surface, which is desirable in some instances for further processing, e.g., printing, floor-performance, easier cleaning, or aesthetics. It also limits surface textures to those that are laterally compressible, but not necessarily aesthetically desirable